astro-ph.HE

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# Title: A turnover in the radio lightcurve of GW170817

Abstract: We present 2--9~GHz radio observations of \object{GW170817} covering the period 125--200 days post-merger, taken with the Australia Telescope Compact Array and the Karl G. Jansky Very Large Array. We see no evidence for evolution in the radio-only spectral index, which remains consistent with optically-thin synchrotron emission connecting the radio, optical, and X-ray regimes. Our observations demonstrate that the radio afterglow peaked at $149\pm2$ days post-merger and is now declining in flux density. The peak implies a total energy in the synchrotron-emitting component of a ${\rm few}\times 10^{50}$ erg. The temporal decay rate is most consistent with mildly- or non-relativistic material and we do not see evidence for a very energetic off-axis jet, but we cannot distinguish between a lower-energy jet and more isotropic emission.
 Subjects: High Energy Astrophysical Phenomena (astro-ph.HE) Cite as: arXiv:1803.06853 [astro-ph.HE] (or arXiv:1803.06853v1 [astro-ph.HE] for this version)

## Submission history

From: Dougal Dobie [view email]
[v1] Mon, 19 Mar 2018 10:03:26 GMT (194kb,D)